Typical wireless communication devices, such as portable telephones, have a phone-book capability, which registers predetermined names, telephone numbers, and other personal information, and quickly reads a series of information as needed. This phone-book capability can allow a user to make a telephone call without searching another medium, such as a printed phone directory or an address book. When a call arrives, it is possible to compare the caller number informed by the caller with the data registered in the portable telephone and display the corresponding name so that the user can know who the caller is before answering the call.
Recently portable video telephones have been proposed which are capable of handling image information. This type of portable video telephone transmits or receives voices and images simultaneously, so that the caller and receiver can talk to each other while viewing the images sent from the opposite parties. Further, this portable video telephone can record an image received while talking or record an image that is taken by a camera incorporated into the video telephone.
Such a portable video telephone can also handle stored image information as information attached to the registered data in the phone book. At the time the phone book is searched for personal information, this capability can permit the user to conduct a search while viewing image information. When a call comes, this capability can display image information together with name information, helping the user understand immediately who the caller is.
There are several ways to retrieve necessary information using the phone-book capability. They include a scheme of allowing a caller to input information (a name or address) associated with a receiver and then retrieving necessary information based on the input information, and a scheme of retrieving necessary information while allowing a user to confirm registered data piece by piece. According to either scheme, when the displayed retrieval result is not the intended one, the intended data is searched by scrolling the displayed information up and down by operating, for example, scroll keys.
At this time, the phone-book capability of this portable video telephone displays attached image information in addition to character information, such as names and telephone numbers. As image information contains a large amount of data, the data quantity is reduced before storage by subjecting the image information to coding such as the one specified by JPEG (Joint Photographic Experts Group). This requires that image information be decoded before it is displayed. The time needed for decoding and displaying an image is longer than the time needed for displaying character information.
As image decoding involves a great deal of work, there is some time delay in displaying the next image. This prevents the user from proceeding to the next search or disables a spontaneous response to the next key operation during the period from the point of the previous search operation to the display of an associated image, thus resulting in a lower operability.
Further, there is a time lag from the display of character information to the display of an associated image. Unless some update control is carried out to maintain the association of character information and image information to be displayed, therefore, the image that has been generated by the immediately previous operation and character information resulting from the current search may be displayed simultaneously, resulting in the mismatching of characters and an image. When character information is displayed after being updated, therefore, it is necessary to erase the image that has been displayed before the update.
Conventionally, when registered data contained an image, a black screen or the like was displayed, as in the case where registered data would contain no image, until the image would be displayed after the display of character information. As the display screen was imageless, such as a black screen, for a while after the display of character information, the user could not determine whether an image corresponding to the displayed character information would be displayed or there was no image corresponding to this character information.